In the manufacture of glass articles, such as glass containers, various anomalies or variations can occur that affect the commercial acceptability of the containers. These anomalies, termed “commercial variations,” can involve one of numerous attributes of the container. For example, commercial variations can include dimensional characteristics of the container at the container bottom or bearing surface, at the container finish, or at the container sealing surface, they can also include variations such as stones or checks within the container finish, sidewall or bottom. It is conventional practice to mold indicia on each container that is indicative of the mold of origin of the container for inspection and quality control purposes. Thus, it is often times useful to provide inspection equipment capable of inspecting the containers for commercial variations, mold indicia or other features that warrant inspection. The term “inspection” is used in its broadest sense to encompass any optical, electro-optical, mechanical or electrical observation or engagement with the container to measure or determine a potentially variable characteristic, including but not necessarily limited to mold codes and commercial variations.
An example of an inspection apparatus is shown in U.S. Pat. No. 3,313,409, which discloses an apparatus for inspecting glass containers in which a starwheel conveys containers in sequence through a series of inspection stations. At one of the inspection stations, container lean is inspected by contacting the bearing surface on the container base with a pair of diametrically opposed rollers. As disclosed in U.S. Pat. No. 4,433,785, the rollers are coupled to linear variable differential transformers (LVDTs) to provide signals as the container is rotated. These signals are processed to indicate departure of the bearing surface from a plane and/or departure from perpendicularity to the axis of rotation. Another apparatus for transporting containers through a series of inspection stations is disclosed in U.S. Pat. No. 6,581,751.
Although the inspection apparatus disclosed in the patents noted above, and assigned to the assignee hereof, have enjoyed substantial commercial success, improvements remain desirable. The rollers are in contact with the container bottom, and are subject to mechanical wear and inaccuracy. The sizes of the rollers may limit the sizes of containers with which they can be employed, and they may affect the size (resolution) of variations that can be detected. It is therefore a general object of the present invention to provide an apparatus and method for inspecting containers that address and overcome the aforementioned deficiencies in the art, and can be used for inspecting the bottom or bearing surface of the container.